This invention relates to a multiplexing device for use in a network system.
A network system is known which comprises main and first through N-th multiplexing devices which are connected to each other in a cascade manner and which carry out communication by a multiplexed signal, where N represents a natural number. The main and the first through the N-th multiplexing devices have main and first through N-th address numbers which are different from each other. The network system further comprises a monitoring device connected to the main multiplexing device so as to monitor the main and the first through the N-th multiplexing devices.
On monitoring one of the main and the first through the N-th multiplexing devices, the monitoring device produces a command signal which includes a command of transferring monitor information from each of the multiplexing devices, together with an address code assigned to each of the multiplexing devices.
Responsive to the command signal given in the form of the multiplexed signal, each of the multiplexing devices produces a monitoring information signal when the address code is coincident with an address number assigned to each multiplexing device. Such a monitoring information signal is located in a prescribed time slot of the multiplexed signal by each multiplexing device to be sent back to the monitoring device.
However, it is impossible to transmit the monitoring information signal from a certain multiplexing device to the monitoring device in case where the prescribed time slot is already used or put in a busy state by another multiplexing device. Therefore, such a certain multiplexing device must inevitably wait for transmission of the monitoring informational signal to the monitoring device until the prescribed time slot becomes vacant or empty. As a result, it is difficult to quickly transmit the monitoring informational sign to the monitoring device.